The present disclosure sets forth an automatic drill pipe wiping system and one which is triggered into operation on retrieving drill pipe so the exterior of the drill pipe does not drip on the rig floor. When drilling a well, drilling fluid is pumped through the drill stem. The drilling fluid is often called mud because it has a strong resemblance to mud. It is forced down through the Kelley, flows through the pipe string the drill collars and out the drill bit at the bottom of the well. It is returned on the exterior of the drill pipe. As the hole is drilled deeper, the drill bit eventually wears out and it is then necessary to remove the drill stem from the well and replace the drill bit. When that occurs, the pipe is pulled one joint at a time until the entire drill stem has been disassembled and stacked in the derrick. Sometimes, three joints are pulled together. When pulling, drilling mud dribbles down the side of the drill pipe and splashes on the rig floor.
U.S. Pat. No. 4,690,213 is a representative pipe wiping device. It shows a mechanism incorporating left and right flexible wiper elements. The wipers have V-shaped edges in them to reach around the pipe so a significant portion of the exterior is wiped. This device is installed at a location where it cannot be seen in operation. Normally it is placed under the rig floor. When a trip is made, it can only be assumed the wiper device is operative. It is switched on or off by the driller at the rig floor. The driller must remember to switch it on and then switch it off when the trip has been completed. This sequence of operations wipes the pipe clean so mud is not splashed on the rig floor.
One aspect of the present disclosure is that the pipe wiping begins with upward movement of the pipe string, and continues with upward movement as long as that movement occurs. The upward movement is detected and transferred to a control system which automatically starts the wiping process. That is detected typically by measuring the mud pump output pressure. A specified threshold pressure is established, and operation above that level forms a signal indicative that the pipe is moving, downwardly either during drilling or is suspended in the well with rotation but without drilling. In this instance pump pressure is maintained high so the flow of mud continues and the well is maintained under control by the mud. When the pressure of the mud pump is reduced, the reduction in mud flow and related pressure in the mud system creates a signal that the pressure is so low that drilling has ended and the drill pipe is being pulled from the well. Wiping is then needed. In an alternative aspect, continued upward movement of the pipe is detected and forms a signal which automatically operates the wiping mechanism.
The wiping mechanism positions a set of air jets around the pipe which blow the mud downwardly. The device includes an air manifold and associated air lines. The lines are constructed and arranged so they blow air on the exterior. While the pipe string is pulled up, air pushes mud down the pipe.
The automatic system of the present disclosure is an improved system enabling pipe wiping (by air blowing on the pipe) to be automatically obtained at a drilling rig. It is summarized as including a pipe wiping mechanism having a set of air jets around the pipe and which are aimed toward the pipe. Operation is occasioned by at pneumatic control console arrangement. It is operated by a low pressure system. The control system is automatic and is triggered by operation by a mechanism which detects upward movement of the pipe. It is either detected directly by measuring movement of the pipe or it is detected by inference by change in rig conditions associated with retrieval of the pipe string. It automatically starts air flow to wipe mud down the pipe.